This invention relates to the production of tubular elastomeric articles which are permanently bent or curved in a desired configuration.
An example of a curved tubular elastomeric article to which this invention relates is an automotive radiator coolant hose. Many of these hoses take on very complex configurations due to multiple bends of varying degrees of curvature and planar attitudes. The customary method of producing this type of hose is to extrude a tube, apply reinforcement to the tube and extrude a cover over the reinforcement. The resultant uncured continuous length of hose is cut to size and pushed onto a cast aluminum mandrel which has the shape of the desired finished hose configuration. A considerable quantity of lubricant is normally employed to facilitate loading the hose onto the mandrel. The loaded mandrel is then placed in a vulcanizer, cured, and the finished hose removed from the mandrel.
Particularly with the more complex hose configurations, loading of the hose onto the rigid mandrel in its uncured state and unloading the hose from the rigid mandrel after cure often introduces stress concentrations at the bends in the hose. A particular problem which may occur upon unloading of the hose from the mandrel after exit from the vulcanizer is known as "hot tear," in which the interior wall of the article actually tears or rips apart or develops holes resulting from abrasive forces. This problem may occur when the operator attempts to remove the hose from a mandrel having sharp bends while the article is still hot.